A sulphur lamp is a highly efficient full-spectrum electrodeless lighting system whose light is generated by sulphur plasma that has been excited by microwave radiation. The technology was developed in the early 1990s, but, although it appeared initially to be very promising, sulphur lighting was a commercial failure by the late 1990s. Since 2005, lamps are again being manufactured for commercial use. The warm-up time of the sulphur lamp is notably shorter than for other gas discharge lamps, with the exception of fluorescent lamps, even at low ambient temperatures. It reaches 80% of its final luminous flux within twenty seconds, and the lamp can be restarted approximately five minutes after a power cut.